The present invention relates generally to wheels and more particularly to a safety device to prevent injury when changing tires on wheels. It is especially useful in preventing injuries due to a mis-matched tire and wheel combination when changing tires with a rim holding tire changer.
It will be appreciated by those skilled in the art of designing and manufacturing equipment used to change the tubeless tires mounted on the wheels, or rims, of cars, trucks and other vehicles that if such equipment is not used correctly and in accordance with instruction, tires can explode and create personal injury and property damage. Manufacturers of such equipment have for years attempted to address this problem with instruction, training manuals, warning decals and hands-on training on their equipment in an attempt to prevent hazards associated with improper use of their equipment. However, not withstanding the efforts made by manufacturers of such equipment to warn and train users, shop mechanics often ignore the training and warnings and use the equipment in a manner contrary to the instructions of the manufacturer. Occasionally, when the rim holding tire changers are used improperly, the results can be catastrophic--an exploded tubeless radial tire that can cause severe personal injury and even death.
U.S. Pat. No. 5,623,981 (Cunningham et al.) Safety Barrier For Rim Holding Tire Changers discloses an excellent device to prevent injury due to improper use of a rim holding tire changer. Improper use of equipment, however, is not the only cause of injuries and property damage. Under the best of conditions, a tire of the wrong size is, occasionally, placed on a rim, i.e. the tire and the rim are mis-matched. The resulting explosion, from an operator attempting to seat, or mount, a mis-matched tire, can be severe. Prior art only reduces the effects of the explosion; it does not reduce the likelihood that an explosion will occur. It is believed that this invention will reduce the likelihood of an explosion occurring.
The type of equipment for which Applicant's invention will be particularly useful is known generally in the industry as a rim holding tire changer. Examples of the type of equipment involved are the rim holding tire changers manufactured by Hennessy Industries, Inc., Applicant's assignee, and marketed under the trademarks "COATS.RTM." and "AMMCO.RTM." including the COATS.RTM. models 5030A and the model 5060A-E and 5060AX-EX. However, there are many manufacturers of such equipment, including FMC Corporation of Chicago, Ill., Corghi of Correggio, Italy and Sice of Correggio, Italy. Equipment of this type has been readily available in the market for many years, is the subject matter of numerous patents and has been described in a variety of publications, bulletins, brochures, operating and instruction manuals, and the like. One such machine is illustrated in the design patent issued to Applicant as co-inventor in U.S. Pat. No. Design 293,916.
The conditions in a tire changing facility are generally not conducive to accurately determining tire and rim sizes. Competition is fierce in the tire changing industry. Customers want tires changed quickly to reduce the time they must wait for their vehicles during service. Shops want tires changed quickly to increase profits; shops charge per job typically, not per hour. Operators, floor mechanics who change the tires, are driven at a harried pace. This leads, inevitably, to mistakes. Car lifts, moving cars, and other moving equipment and hoses create moving shadows, even with the use of modern lighting fixtures. Moving shadows make it difficult to make a quick determination of tire and wheel sizes. Dirt and grease further reduce the likelihood of accurate determinations of tire and rim sizes. Loud machinery makes concentration difficult as well. These and other factors make quick and accurate determination of tire and wheel sizes difficult, to say the least. Nothing in the prior art aids this determination. Lack of accurate size determination inevitably leads to accidents.
When accidents occur, lawsuits generally follow. Regardless of the efforts of the manufacturers to train users of their equipment in the proper use of rim holding tire changers, teach proper identification procedures, or improve working conditions, the cost of defending such claims can be enormous. In addition, there have been some occasions where damages have been awarded under product liability theories on the basis that the manufacturer of the equipment could have "done more" to protect the user of the equipment against injury.
The particular safety problem involved generally arises during the bead seating step of the tire changing process and in those occasions where there are mis-matched tires and wheels. In the automobile industry in the U.S., practically all rim contours conform to standards established by the Tire and Rim Association, Inc. FIG. 1 illustrates a tire T to be mounted on a rim R. FIG. 2 shows a cross section of a typical rim R, including an upper rim lip 10, a lower rim lip 20, an upper annular hump 30, and a lower annular hump 40. The rim R also, typically, includes a drop center 35, and a rim surface interior 45. The rim surface interior 45 faces outward toward the interior of the tire, and is covered when the tire is mounted on the rim. For ease of description, the upper and lower humps, 30 and 40, will be referred to generally as hump H, and the upper and lower lips, 10 and 20, will be referred to generally as lip L, unless otherwise specified. FIG. 3 shows a cross section of the tire T, including a tire interior, or chamber, 60, and a bead 70.
FIG. 2 also illustrates a typical asymmetrical rim contour for a drop center rim for 13", 14", 15", 16", 17", etceteras diameter tire designations. Symmetrical rim contours are also commonly used in the industry. The annular hump H serves as a safety feature to keep the inner perimeter of the tire from slipping into the drop center of the rim during certain operations of the vehicle. The hump H, which is employed in the majority of modern rim contours, creates a problem in the mounting of a new tire since the bead 70 of the tire T must ride over the hump H and the outside diameter of the hump H is greater than the inside diameter of the tire. To deal with this problem in the tire mounting process, the bead 70 of the tire must first be sealed against the hump H in order to fill the chamber 60 of the tire T with compressed air. As compressed air is injected into the chamber 60, the bead 70 will ride over the hump H and seat against the "j" contour of the perimeter of the rim. After the bead 70 is properly seated, the tire T can be inflated to the recommended pressure and the rim is ready to be attached to the hub of the car.
Danger occurs when the bead 70 binds against the hump H and does not ride over it to seat against the rim lip L. When this happens, contrary to instructions and warnings, mechanics tend to continue to force compressed air into the tire chamber far beyond the recommended pressure of approximately 40 psi for a standard automobile tire. As the pressure within the chamber 60 continues to build up, the mechanic often will peer over the tire to see if the bead 70 has seated against the rim lip L. When the bead 70 actually does ride over the hump H, the pressure within the chamber 60 of the tire can cause the bead 70 to accelerate at a tremendous rate and be impelled against the rim lip L. The force of the bead 70 against the rim lip L can cause the tire T, or the rim R, or both, to explode and if the mechanic is peering over the tire, the explosion occurs in his face and can cause tremendous injury, or even death.
The other occasion which can create the type of problem discussed above is when a mechanic attempts to mount a mis-matched tire/rim combination, i.e. mount the wrong sized tire on a rim.
Automobile tires are generally mounted on even sized wheels of 14", 15", 16", 17", etc. The automobile industry for a number of years used half-sized rims on small trucks such as pick-up trucks. Thus, the trucks would have rim diameters of 16.5", 17.5", etc. In the early 1980's, 16" tires on pick-up trucks became popular and the 16.5" tires lost favor because of extra expense, etc. However, in the older pick-up trucks, the customer would have a 16.5" rim and when he took his pick-up truck to a tire dealer to have a new set of tires mounted on his truck, occasionally a mechanic would pull a 16" tire from inventory and mount a 16" tire on a 16.5" rim (the 16" tire on a 16.5" rim is the predominant problem of mis-matched tires although the problem could occur in other sized rim/tire combinations such as the attempt to mount a 17" tire on a 17.5" rim, etc.).
Some common, or known, mis-matched combinations include the following dimensions: [13 in .vertline.365 mm]; [14 in .vertline.390 mm]; [14 in .vertline.14.5 in]; [15 in .vertline.15.5 in]; [16 in .vertline.16.5 in]; [17 in .vertline.17.5 in]; [19 in-19.5 in]; [22 in .vertline.22.5 ; in]; and [24 in .vertline.24.5 in]. Note that diameters measured in metric units can easily be mis-matched with diameters measured in inches. Additionally, mis-matches involving diameters such as [16.5 in .vertline.17 in] can occur. Possible mis-match combinations are only limited by the operators attentiveness, or lack of attentiveness. For example, a 22 inch diameter could be mis-matched with a 24 inch diameter. Since one cannot predict what possible mis-match combinations will occur, this invention can serve as a warning to prevent other possible mis-matches.
Mounting an even sized tire on a half-sized wheel simply is not possible.
Refer to FIG. 5 which illustrates an even sized tire T on a half-sized rim R.
The bead 70 of a 16" tire T will not seat properly on a 16.5" rim R, or wheel, and continuing to apply compressed air into the chamber 60 of a tire T will eventually result in an explosion of the tire or the tire and the wheel. The enlargement in FIG. 5 shows a 15 degree bead seat, rather than a 5 degree bead seat. If the mechanic is peering over the tire T to see if the bead 70 is properly seated, he will in all likelihood be severely injured. FIG. 6 illustrates a half-sized tire T on and even sized rim R. Again, proper bead 70 seating is not possible, tire explosion, however, is. The enlargement in FIG. 6 shows the gap between the rim interior surface 45 and the tire bead 70.
Prior art lacks a mechanism by which an operator may readily, under typical shop conditions, match a tire size to a rim size. What is needed is a way for an operator to readily distinguish between tires, and rims, of different sizes. After being subjected to noises caused by hammering, air guns, and other machinery, for eight hours in a light deficient and gas fume filled environment. Under the demands of such a fast paced job, an operator needs a clear, simple, conspicuous way to avoid mis-matching tires and rims. The operator needs a measure of safety lacking in the prior art; and the shops would like a way to lower costs associated with exploding tires. Applicant believes the present invention provides a simple and elegant solution to these problems.